What is the URL scheme that is used by Bitcoin to copy transaction information directly into the client? Which versions of Bitcoin clients support it?
The Bitcoin Improvement Proposal that defines the Bitcoin URI scheme is BIP21.
The simple syntax is:
On the desktop all of Armory, Electrum and MultiBit respond to Bitcoin URI clicks in a browser and I believe Bitcoin-QT V0.7 does as well.
On mobiles Android Bitcoin Wallet does. On the iPhone the blockchain.info app does.